wrote in message
...
In uk.d-i-y, Dave Jones wrote:

As you Joining 10 mm cable you really need to use a connection block of
greater than 65 Amps, i.e. same rating as the cable.

Really? I Think You'll Find that sizing according to the overcurrent
device - a 45A presumably-type-B MCB, in this case - is the relevant
design procedure. One could plausibly argue that the lower load current
of 40A (9.6kW/240V - yes, 240V not 230V since the 230 figure is a
regulatory fiction and should the supply drop to 230V in some distant
future the load drawn by the heater elements will also drop) for the
fixed-equipment shower, which has no way of producing an overload, could
be used as the circuit design current: but that's a bit of margin-shaving
in which the sensible person would not indulge. But sizing for a 65A
current throughout, when the 10mmsq cable has been selected to give a
decent margin for voltage-drop/earth-loop-impedance/passing-thru-thermal-
insulation or whatever, rather than the "might just do it on a good day
with the wind in the right direction" use of 6mmsq, is over-egging in
the other direction.

Stefek

My understanding was that if you have a any cable which requires a join,
that join should be of equivalent rating to the cable. Other wise if Ross
sells up in 2 years, job bloggs moves in, sees 10mm in consumer unit,
upgrades the fuse and installs a 12kw shower, not knowing about the under
rated junction box in the loft. Get's up in the morn, he has shower, wife
has shower, kids have shower, come home house burned down!

Dave